Seeding of synthetic amyloid-β(1-42) monomers by amyloid-β(1-42) present in Alzheimer’s brains Pubblico
Kim, Ashley (Spring 2024)
Abstract
As aggregates of the self-assembling amyloid-beta(1-42) peptide (Aβ42) become increasingly
popular targets in the search for Alzheimer’s disease (AD) therapeutics, it is especially critical to
further understand the aggregation mechanism and characterize the resulting three-dimensional
structures. Prior studies have semi-selectively extracted Aβ42 aggregates out of brain samples
from AD patients and characterized them with negative staining and cryo-EM. Helical Aβ42
fibrils can be identified, but the smaller oligomers that are believed to be the toxic agents remain
elusive. In this work, we aim to investigate the oligomerization and subsequent fibrillization of
Aβ42 in correlation to disease by releasing synthetic rhodamine-labeled Aβ42 (Rho-Aβ42)
monomers into AD brain extract. The solid-state monomers were dissolved into brain extract and
co-incubated over a 1-day period, theoretically allowing for co-aggregation to occur between
synthetic and natural Aβ42 where pre-existing Aβ42 fibrils serve as “seeds” for Rho-Aβ42
addition. Rho-Aβ42 was incubated in both “slow”-progressing and “rapid”-progressing AD
extract, along with a neutral salt buffer containing no brain matter. All samples were examined at
three time-points (t=0 hr, 3 hr, 24 hr) by negative stain transmission electron microscopy. We
found notable differences between the structures of Aβ42 fibrils formed in buffer and brain
extract conditions, emphasizing the need to consider the role of other brain components in
aggregation regardless of self-assembling properties. Subsequent studies will aim to track the
synthetic Aβ42 monomers during their incorporation into brain aggregates using fluorescence
microscopy, as they were synthesized with N-terminal Rhodamine B tags.
Table of Contents
Introduction………………………………………………………………………………………..1
Background………………………………………………………………………………………...5
Methods…………………………………………………………………………………………....10
Results……………………………………………………………………………………………...12
Discussion………………………………………………………………………………………....18
References………………………………………………………………………………………..24
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